Diuretic state affects ascending thin limb tight junctions

Sonntag, Svenja Rebecca, Ziemens, Annalisa, Wulfmeyer, Vera Christine, Milatz, Susanne, Bleich, Markus and Himmerkus, Nina (2018) Diuretic state affects ascending thin limb tight junctions American Journal of Physiology-Renal Physiology, 314 (2). F190-F195. DOI 10.1152/ajprenal.00419.2017.

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Abstract

The nephron segments in the inner medulla are part of the urine concentrating mechanism. Depending on the diuretic state, they are facing a large range of extracellular osmolality. We investigated whether water homeostasis affects tubular transport and permeability properties in inner medullary descending thin limb (IMdTL) and ascending thin limb (IMaTL). Three experimental groups of rats under different diuretic states were investigated on metabolic cages: waterload, furosemide-induced diuresis, and control (antidiuresis). Urine production and osmolalities reflected the 3-day treatment. To functionally investigate tubular epithelial properties, we performed experiments in freshly isolated inner medullary thin limbs from these animals. Tubular segments were acutely dissected and investigated for trans- and paracellular properties by in vitro perfusion and electrophysiological analysis. IMdTL and IMaTL were distinguished by morphological criteria. We confirmed absence of transepithelial electrogenic transport in thin limbs. Although diffusion potential measurements showed no differences between treatments in IMdTLs, we observed increased paracellular cation selectivity under waterload in IMaTLs. NaCl diffusion potential was −5.64 ± 1.93 mV under waterload, −1.99 ± 1.72 mV under furosemide-induced diuresis, and 0.27 ± 0.40 mV under control. The corresponding permeability ratio PNa/Cl was 1.53 ± 0.21 (waterload), 1.22 ± 0.18 (furosemide-induced diuresis), and 0.99 ± 0.02 (control), respectively. Claudins are main constituents of the tight junction responsible for paracellular selectivity; however, immunofluorescence did not show qualitative differences in claudin 4, 10, and 16 localization. Our results show that IMaTLs change tight junction properties in response to diuretic state to allow adaptation of NaCl reabsorption.

Document Type: Article
Research affiliation: Kiel University
Kiel University > Kiel Marine Science
OceanRep > The Future Ocean - Cluster of Excellence
Refereed: Yes
DOI etc.: 10.1152/ajprenal.00419.2017
ISSN: 1931-857X
Projects: Future Ocean
Date Deposited: 02 Feb 2018 11:23
Last Modified: 02 Feb 2018 11:23
URI: http://eprints.uni-kiel.de/id/eprint/41800

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